Скачать или смотреть Fixing the Error Screen When Loading SharedPreferences in Flutter

Learn how to solve the error encountered while loading SharedPreferences in your Flutter app, specifically for the method getStringList called on null.
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Troubleshooting SharedPreferences in Flutter: Resolving the Error Screen

If you're developing a Flutter app and using SharedPreferences for data storage, you might encounter an error screen while trying to load your saved preferences. One common issue developers face is the error message: “The method getStringList was called on null.” Let's dig into what causes this error and how you can fix it effectively.

Understanding the Problem

In the context of Flutter, SharedPreferences allows you to save simple data types persistently. If you're attempting to access saved data in your build method before it has been fully initialized, you can end up trying to call methods on a null object. This typically results in the error you're seeing.

Example Scenario

Consider the following code snippet that demonstrates the issue. It initializes SharedPreferences in the initState method but attempts to access the data directly in the build method without ensuring that the SharedPreferences instance is ready.

[[See Video to Reveal this Text or Code Snippet]]

The Solution

The error arises because SharedPreferences might not be completely initialized when the build method is called. Here’s a structured approach to resolve the issue:

Use FutureBuilder

To handle asynchronous data fetching more effectively, the FutureBuilder widget is the ideal tool. Here's how you can incorporate it into your code:

[[See Video to Reveal this Text or Code Snippet]]

Key Points to Note:

FutureBuilder: This widget simplifies working with asynchronous data in your UI. It manages the state of the data fetching process automatically.

Null Safety: By checking if snapshot.hasData, you can ensure that SharedPreferences is available before calling any methods on it.

Fallbacks: Using an empty list [] in case of null helps avoid crashes.

Conclusion

In summary, if you encounter the Error screen when loading SharedPreferences in your Flutter app, ensure that your data accesses are done after confirming that the data is ready with tools like FutureBuilder. This approach will provide a smoother user experience and prevent runtime errors associated with null values. Happy coding!